Pinnixa tubicola Holmes 1894

Tubes of tubeworms such as Chaetopteris and Terebellids; tubes of Neotrypaea californiensis.

Depth Range: Intertidal to 57 m

As with all members of Family Pinnotheridae, this crab is small, has no rostrum, and has an oval, circular, or sqared-off carapace which has no teeth either between the eyes or along the anterolateral margin plus lives symbiotically. This species has a very wide carapace, 2x to 2.5x as wide as long. The third pair of walking legs is longest. The propodus of legs 3-5, especially of leg 3, are longer and much wider than the dactyl. Walking leg 4 has no long setal fringe and the posteroventral margin of the ischium of walking leg 4 has no tubercles. The telson is wider than long and distally curved. Color a pattern of light and dark brown, gray, and some white. Chelipeds are white with patches of brown, red, or orange with white tips. Walking legs are white with dark brown streaks and blotches. Cornea red with gold flecks.

How to Distinguish from Similar Species: Of pinnotherid species with carapaces more than 1.5x as wide as long, this species differs from P. faba and P. littoralis because those species have curved dactyls. It differs from P. eburna, P. occidentalis, and P. schmitti because those species do not have a propodus of legs 3-5 clearly longer than their dactyl. It differs from P. longipes because P. longipes has a long setal fringe on walking leg 4 and tubercles on the posteroventral margin of the ischium of walking leg 4.

Biology/Natural History: Lives in polychaete worm tubes such as Chaetopterus and Terebellids. Several other very similar pea crab species do as well, such as juveniles of P. franciscana. Frequently in pairs in the worm tube. Ricketts et al. state that only males of this species have been found ranging outside of the tubeworm burrow, and that rarely. This species is widespread but is often overlooked.

Geographical Range: Prince Rupert, BC to Mexico